A slot waveguide is an optical waveguide that guides light and strongly confines the guided light by capitalizing on the discontinuity of an electric field at high-refractive-index-contrast interfaces. A slot waveguide typically includes two regions of high-refractive-index material separated by a gap, or slot, having a low-refractive-index. The high-refractive-index material is typically covered by a cladding material.
Nonlinear electrooptic polymers can be used as a cladding material and can also be simultaneously incorporated into the slot of the slot waveguide. Basically, the use of such materials allows for a sufficiently high power flux (or “fluence,” a term of art) in the material by exciting nonlinear behavior, meaning that the properties of the material change with the input optical power. This kind of effect is very often described through the use of, for instance Chi2 (χ2) and Chi3 (χ3) which are material dependent constants that describe the strength of two of the relevant nonlinear optical activities of a material. Some nonlinearities, which are material dependent, will work at the full optical frequency, while others are slower. Recently, engineered organic materials have begun to be used for nonlinear optics, because they can be designed to have extremely large χ2 and χ3 moments.